1. Field of the Invention
The present invention relates to an image processing apparatus and method, a program and a medium storing thereon the program, and particularly to an image processing apparatus and method, a program, and a medium storing thereon the program, all configured to enable taken images to be processed more naturally and sharply.
2. Description of Related Art
An imaging device used in digital still cameras and digital video cameras with less incident light exhibits poorer S/N (Signal-to-Noise ratio). Noise can be classified into random noise and fixed pattern noise (FPN). Since the random noise is not position-dependent, it can be cancelled and reduced by adding a plurality of images.
However, when the plurality of images are added, there is a problem that the added resultant image is blurred due to unsteady hold on the camera or object movement. To overcome this situation, a technique is considered, in which motion vectors are obtained for each of images and the images are added according to their motions, whereby to reduce noise, without having blurring due to unsteady hold on the camera or object movement.
What is problematical in this technique is occlusion and exposure occurring within an image. An occluding area in the image is an area where, e.g., a foreground moves in a manner covering a background, whereas an exposing area is an area where the background reveals from the foreground.
Neither occluding nor exposing areas occur as long as all parts of the image move in the same manner. However, in a scene including a locally different motion, an occluding area and an exposing area occur. In either case of the occluding and exposing areas, when images are added according to their motion vectors, conflicts occur within a resultant image, making the resultant image unnatural.
In one exemplary method, an occluding area and an exposing area are detected by obtaining a standard deviation of luminance in a local area on a frame basis, and then by tracing motion vectors to find any change in standard deviation values, i.e., by checking if there is any such change per frame. This method has been proposed by Ben-Ezra et al.
Also, in another method (see Published Translation of International Patent Application No. 2005-517251, Patent Document 1), three areas, namely, an occluding area, a non-occluding area, and an emerging area, are defined by using preceding and succeeding frames, and the occluding area is interpolated from a frame that is one frame earlier, and the emerging area is interpolated from a frame that is one frame later.